Incision integrity and postoperative outcomes after microcoaxial phacoemulsification performed using 2 incision-dependent systems

ARTICLE

Incision integrity and postoperative outcomes after microcoaxial phacoemulsification performed using 2 incision-dependent systems Vaishali Vasavada, MS, Abhay R. Vasavada, MS, FRCS, Viraj A. Vasavada, MS, Samaresh Srivastava, DNB, Devarshi U. Gajjar, MSc, PhD, Siddharth Mehta, DO

PURPOSE: To compare incision integrity and clinical outcomes of 2 microcoaxial phacoemulsification systems. SETTING: Iladevi Cataract & IOL Research Centre, Ahmedabad, India. DESIGN: Prospective randomized clinical trial. METHODS: Eyes were randomized to have phacoemulsification using a 1.8 mm clear corneal incision (CCI) system (Group 1, Stellaris system) or a 2.2 mm CCI system (Group 2, Intrepid Infiniti system). Incision enlargement at end of surgery was measured. At the conclusion of surgery, trypan blue was applied over the conjunctival surface, anterior chamber aspirate withdrawn, and ingress into anterior chamber measured. Postoperative observations included evaluation of the CCI using anterior segment optical coherence tomography (AS-OCT), change in central corneal thickness (CCT), and anterior segment inflammation at 1 day, 1 week, and 1 month and endothelial cell loss and surgically induced astigmatism (SIA) at 3 months. RESULTS: Incision enlargement (P<.001) and trypan blue ingress in the anterior chamber (mean 1.7 log units G 0.6 [SD] versus 3.8 G 0.6 log units, P<.001) was significantly greater in Group 1 (n Z 50) than in Group 2 (n Z 50). On AS-OCT, endothelial misalignment and gaping were more frequent in Group 1 at 1 day (PZ.001) and 1 week (PZ.018). There were no significant differences in SIA, change in CCT, endothelial cell loss, or anterior segment inflammation (P>.05). CONCLUSION: At the end of surgery, it is not the initial incision size alone but also the distortion of the incision during subsequent stages of surgery that determine the integrity of the CCI. Financial Disclosure: Iladevi Cataract & IOL Research Centre receives occasional travel support from Alcon Laboratories, Inc. No author has a financial or proprietary interest in any material or method mentioned. J Cataract Refract Surg 2013; 39:563–571 Q 2013 ASCRS and ESCRS

With improvements in phacoemulsification machines and surgical techniques and with newer IOL delivery systems, the size of the clear corneal incision (CCI) is progressively decreasing. The advantages of small incisions during cataract surgery are well known and include reduced surgically induced astigmatism (SIA), reduced intraoperative and postoperative inflammation, and faster visual rehabilitation.1,2 With widespread adoption of smaller incision phacoemulsification techniques, microcoaxial phacoemulsification has gained popularity3,4 However, wound integrity could be a concern when using very small incisions. Smaller incisions are not necessarily better. These incisions require the use of Q 2013 ASCRS and ESCRS Published by Elsevier Inc.

compatible instrumentation and IOL delivery systems to avoid thermal injury, wound distortion, and corneal hydration. At present, there are 2 popular systems for performing microcoaxial phacoemulsification: the 2.2 mm incision system and the 1.8 mm incision system, both available on 2 different platforms. Both approaches have been reported to be safe and effective during emulsification of age-related cataracts.5,6 In a previous randomized experimental trial,A we found that stromal collagen denaturation and damage were greater when microcoaxial phacoemulsification was performed through a 1.8 mm incision than through a 2.2 mm incision. 0886-3350/$ - see front matter http://dx.doi.org/10.1016/j.jcrs.2012.11.018

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Luo et al.6 questioned the integrity of the 1.8 mm incision compared with that of the 2.2 mm incision. However, there is not enough information in the literature comparing incision integrity and postoperative outcomes after microcoaxial phacoemulsification with 1.8 mm and 2.2 mm incisions. The aim of this study was to compare the incision integrity and postoperative outcomes after microcoaxial phacoemulsification with 2 popular systems using 1.8 mm and 2.2 mm incisions. PATIENTS AND METHODS This prospective randomized patient- and analyzer-masked clinical trial comprised patients with uncomplicated age-related cataract having phacoemulsification at Iladevi Cataract & IOL Research Centre, Ahmedabad, India, from September 2011 to February 2012. The study was approved by the institutional review board, and informed consent was obtained from all the patients before enrollment. The study followed the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use good clinical practice guidelines. The study is registered with clinicaltrials.gov (NCT01385878).B Patients having nuclear or corticonuclear cataracts of grade 2 to 4 according to the Lens Opacities Classification System III were included.7 The following were the exclusion criteria: glaucoma, shallow anterior chamber (anterior chamber depth !2.1 mm), pupil dilation less than 6.0 mm, extremely dense cataract, posterior polar cataract, subluxated cataract, white mature cataract, diabetic retinopathy, high myopia (defined as axial length O25 mm), uveitis, or previous ocular trauma or surgery. Patients were randomized to 1 of 2 groups based on the incision size and phacoemulsification system used. In Group 1, microcoaxial phacoemulsification was performed through a 1.8 mm CCI with the Stellaris PC system (Bausch & Lomb) using longitudinal ultrasound. In Group 2, microcoaxial phacoemulsification was performed through a 2.2 mm CCI with the Infiniti Vision system (Alcon Laboratories, Inc.) using torsional ultrasound.

Surgical Technique All surgeries were performed by the same experienced surgeon (A.R.V.), who was familiar with both systems. An initial 1.0 mm corneal paracentesis incision was created, followed by injection of a dispersive ophthalmic viscosurgical device (OVD) and cohesive OVD as per the soft-shell

Submitted: August 7, 2012. Final revision submitted: October 5, 2012. Accepted: November 2, 2012.

technique.8 A single-plane temporal CCI was made with an internal entry length of at least 1.5 mm. The internal entry in all eyes was measured using calipers (Titanox) that measure length in steps of 0.1 mm. An anterior capsulorhexis was created using a cystotome and microcapsulorhexis forceps (American Surgical Instruments Corp.). Multiquadrant cortical-cleaving hydrodissection was performed. Phacoemulsification was performed using a standardized technique.3,9,10 Standardized parameters for emulsification were used in both groups depending on the grade of nuclear sclerosis (Table 1). Bimanual irrigation/aspiration (I/A) was performed for cortex removal. In all eyes, a single-piece foldable intraocular lens (IOL) was injected in the bag using an injector system compatible with the incision and without enlarging the main incision. The OVD was aspirated using bimanual I/A. Postoperatively, all patients used topical steroid eyedrops 4 times a day for 2 weeks, after which the regimen was tapered by 1 drop for 3 weeks. In Group 1, a 1.8 mm temporal CCI was made using a 1.8 mm laser-edge steel trapezoidal knife (Bausch & Lomb). A sleeved 1.8 mm C-MICS tip (Bausch & Lomb) was used. Longitudinal ultrasound was used in the pulse mode. Dual linear footpedal control available on the machine was used. An MI60 IOL (hydrophilic acrylic, Bausch & Lomb) was implanted in the capsular bag using a Viscoject 1.8 injector system (Medicel AG) with a Viscoglide cartridge. For the Infiniti system, a 2.2 mm temporal CCI was made using a 2.2 mm anterior bevel Intrepid knife (Alcon Laboratories, Inc.). A 0.9 mm mini-flared 45-degree ABS Kelman tip was used with an Ultrasleeve (Alcon Laboratories, Inc.). Torsional ultrasound was used in the pulse mode. An Acrysof SN60WF IOL (hydrophobic acrylic, Alcon Laboratories, Inc.) was implanted in the capsular bag using a Royale III injector (American Surgical Instruments Corp.) and D-cartridge (Alcon Laboratories, Inc.). The incision width was measured using an incision gauge (Titanox) measuring in steps of 0.1 mm at the following time points: after incision creation, after phacoemulsification, and after IOL implantation. The total surgical time (defined as the time from beginning of sculpting to end of last quadrant removal) and the volume of a balanced salt solution (BSS, Alcon Laboratories, Inc.) used from the beginning of surgery to the end of nuclear quadrant removal were recorded at the end of surgery in both groups. At the end of cataract surgery, stromal hydration was performed on all the incisions. After hydration of the incisions, the speculum was removed from the eye. Thereafter, trypan blue 0.0125% (pH Z 7.39, osmotic pressure Z 1.22) (Shah & Shah) was applied over the conjunctival surface using a micropipette. After a waiting period of 2 minutes, the surface was irrigated with balanced salt solution to wash away the residual trypan blue on the ocular surface. Anterior chamber aspirates of 0.1 mL were obtained in all eyes using a 27-gauge cannula mounted on a tuberculin syringe through the paracentesis. Trypan blue levels were measured from this aspirate. After the aspirate was taken, the speculum was reinserted and 0.1 mL of preservative-free moxifloxacin (Vigamox) was injected into the anterior chamber.

From Iladevi Cataract & IOL Research Centre, Ahmedabad, India. Presented in part at the ASCRS Symposium on Cataract, IOL and Refractive Surgery, Chicago, Illinois, USA, April 2012.

Quantifying Trypan Blue Ingress

Corresponding author: Abhay R. Vasavada, MS, FRCS, Iladevi Cataract & IOL Research Centre, Ahmedabad, India. E-mail: icirc@ abhayvasavada.com.

Trypan blue measurements were obtained as described in a previous publication.11 An ultraviolet visible spectrophotometer (Perkin Elmer, Lambda 25) was used to measure the optical density of the trypan blue solution. The dilution

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Table 1. Ultrasound and aspiration parameters during phacoemulsification. Group 1 (n Z 50)

Group 2 (n Z 50)

Longitudinal US in pulse mode; 60% preset power; 40 pulses/s; 60% on time 120 90 d

Torsional US in pulse mode; 60% preset amplitude; 40 pulses/s; 60% on time 100 50 20

Longitudinal US in pulse mode; 60% preset power; 40 pulses/s; 60% on time 200 to 400 (depending on nuclear sclerosis grade)

Torsional US in pulse mode; 60% preset amplitude; 40 pulses per second; 60% on time 200 to 400 (depending on nuclear sclerosis grade) 50 20

Step Sculpting Ultrasound energy Vacuum (mm Hg) Bottle height (cm) Aspiration flow rate (cc/min) Chopping Ultrasound energy Vacuum (mm Hg) Bottle height (cm) Aspiration flow rate (cc/min) Quadrant removal Ultrasound energy Vacuum (mm Hg)

90 d Longitudinal US in pulse mode; 60% preset power; 40 pulses/s; 60% on time; dual linear foot control used Up to 400 (depending on nuclear sclerosis grade)

Bottle height (cm) Aspiration flow rate (cc/min)

100 d

Torsional US in pulse mode; 60% preset amplitude; 40 pulses/s; 60% on time Up to 400 (depending on nuclear sclerosis grade) 90 20

US Z ultrasound

factors were then converted into log values that were used for statistical analysis. The Mann-Whitney test and Kruskal Wallis test were used to statistically compare the values between the 2 groups.

generalized/localized epithelial edema. Monocular uncorrected distance visual acuity (UDVA) at 1 day and corrected distance visual acuity (CDVA) at 3 months were compared between the groups.

Intraoperative Outcome Measures

Incision Morphology on Anterior Segment Optical Coherence Tomography

The amount of trypan ingress into the anterior chamber, volume of balanced salt solution used, cumulative dissipated energy (CDE), and total surgical time were compared between the 2 groups.

Postoperative Outcome Measures The central corneal thickness (CCT) was measured using ultrasonic pachymetry (Ocuscan, Alcon Laboratories, Inc.) preoperatively and postoperatively at 1 day, 1 week, and 1 month. The percentage change in CCT from preoperatively was calculated as follows: (preoperative postoperative)/ preoperative  100. Manual keratometry was performed preoperatively and postoperatively at 3 months using an OMS-4 keratometer (Topcon). The SIA was calculated using the 3-month postoperative keratometric power and vector analysis. The corneal endothelium was evaluated by measuring the endothelial cell density (ECD) and coefficient of variation (CoV) preoperatively and 3 months postoperatively. Endothelial cell loss was defined as follows: percentage of endothelial cell loss Z (preoperative postoperative )/preoperative  100. Endothelial cell counts in the central cornea were performed using a noncontact specular microscope (SP 2000P, Topcon Corp.). Anterior segment inflammation was graded at the slitlamp at 1 day, 1 week, and 1 month using Hogan's criteria12 for grading anterior chamber cells and flare. Corneal clarity was graded at the slitlamp as the presence of Descemet folds (generalized/localized, centrally/localized close to incision) and the presence of

The morphology of the temporal CCI was evaluated using anterior segment optical coherence tomography (AS-OCT) (Visante, Carl Zeiss Meditec AG) 1 day, 1 week, and 1 month postoperatively. A high-resolution mode was used to capture images. Scans 10.0 mm long and 3.0 mm deep were taken with an 18.0 mm optical axial resolution and 60.0 mm transversal resolution. The eye position and the location of the cross-section were verified by a chargecoupled device camera. The following were analyzed on the image: (1) incision angle (angle between the line that joins the epithelial and endothelial ends of the incision and the tangential line on the corneal surface), (2) existence of a gap on the epithelial side of the incision, (3) presence of a gap or misalignment on the endothelial side of the incision, (4) local Descemet membrane detachment, and (5) corneal thickness 1.0 mm temporal to the incision. These examinations were performed by 1 of 2 trained examiners, both masked to the patients' group assignment.

Sample-Size Calculation A sample size of 100 patients was computed using observations from a pilot study of 10 patients in each of the 2 phacoemulsification technique groups. The concentration of trypan blue in the anterior chamber aspirate was the primary outcome measure. A difference of 0.175 log units or

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Table 2. Comparison of Intraoperative parameters between groups. Mean G SD Parameter Total surgical time CDE (%) Volume of balanced salt solution (cc)

Group 1 (1.8 mm Incision)

Group 2 (2.2 mm Incision)

P Value*

7.4 G 1.12 20.6 G 7.86 67.92 G 20.2

5.29 G 1.26 18.67 G 5.11 62.5 G 8.2

!.0001 .07 .062

CDE Z cumulative dissipated energy *P!.05 statistically significant

more was considered relevant in this study. A sample size of 50 patients in each group would have an 80% power to capture the above-mentioned difference between the 2 groups.

Statistical Analysis Statistical analysis was performed using SPSS software (version 12, SPSS, Inc.) and the Mann-Whitney test, Fischer exact test, and Student t test. A P value less than .005 was considered statistically significant.

implantation was significantly greater in Group 1 than in Group 2 (P!.0001) (Figures 1 and 2). With further analysis, enlargement from the initial incision to the end of phacoemulsification was significantly greater in Group 1 than in Group 2. However, incision enlargement from the end of phacoemulsification to the end of IOL implantation was comparable between the groups.

RESULTS

Trypan Blue Ingress into the Anterior Chamber

The study enrolled 100 patients, 50 in each group. The mean age of the patients was 64.42 years G 5.43 (SD) in Group 1 and 62.67 G 8.79 years in Group 2 (PZ.52). The male-to-female ratio was 0.92 in Group 1 and 1.04 in Group 2 (PZ.73). No patients were lost to follow-up. The mean grade of nuclear sclerosis in Group 1 and Group 2 was comparable (3.01 G 0.65 and 3.11 G 0.50, respectively; PZ.67).

Table 4 shows the mean logs of denominators of trypan blue in the anterior chamber. The lower log values indicate higher trypan blue content in the aspirate and therefore a higher level of ingress into the anterior chamber originating from the ocular surface. The difference in the mean measurements between groups was statistically significant (P!.0001). Group 1 had significantly greater ingress of trypan blue than Group 2.

Intraoperative Parameters Table 2 shows the total surgical time, CDE, and volume of balanced salt solution used. The total surgical time was significantly greater in Group 1 than in Group 2 (P!.0001). The volume of balanced salt solution used and the CDE were comparable. Incision Enlargement Table 3 shows the mean incision sizes. Incision enlargement from the initial incision to the end of IOL

Surgically Induced Astigmatism Although the magnitude of SIA was greater in Group 1, the difference between the groups was not statistically significant at 3 months. The mean magnitude of SIA was 0.77 G 0.63 D in Group 1 and 0.48 G 0.42 D in Group 2 (PZ.13, Mann Whitney test). The mean axis of SIA was 105.9 G 55.52 degrees and 88.15 G 44.32 degrees, respectively (PZ.13, Mann-Whitney test).

Table 3. Incision width comparison between groups at different times. Mean G SD Parameter Incision width after phacoemulsification Incision width after IOL implantation Enlargement from initial incision to end of phacoemulsification Enlargement from end of phacoemulsification to end of IOL implantation Enlargement from initial incision to end of IOL implantation

Group 1 (nZ 50)

Group 2 (n Z 50)

P Value

1.97 G 0.06 2.05 G 0.05 0.16 G 0.04 0.08 G 0.07 0.36 G 1.56

2.21 G 0.03 2.29 G 0.02 0.01 G 0.03 0.07 G 0.04 0.25 G 0.05

d d !.0001 .97 !.0001

IOL Z intraocular lens

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Figure 1. Top: Incision width of 1.8 mm after initial incision. Bottom: Incision enlarged to 2.1 mm after IOL implantation.

Figure 2. Top: Incision width of 2.2 mm after initial incision. Bottom: Incision enlarged to 2.3 mm after IOL implantation.

Anterior Segment Optical Coherence Tomography: Incision Morphology

Descemet detachment in Group 2 than in Group 1 at 1 day and 1 week. The difference was not statistically significant. At the end of 1 month, 5 eyes in Group 1 had localized Descemet detachment at the incision site whereas no eye in Group 2 had a persistent Descemet detachment.

Table 5 shows the qualitative incision morphologic features on AC-OCT in both groups. Localized Descemet Membrane Detachment There was no statistically significant difference in the incidence of localized Descemet detachment at 1 day, 1 week, or 1 month (Figure 3). More eyes had localized

Endothelial Gaping or Misalignment Significantly more

eyes had gaping or misalignment of the endothelium

Table 4. Between-group omparison of log of denominators of trypan blue ingress into the anterior chamber after IOL implantation between the 2 groups (P!.0001, Mann-Whitney U test). Log of Denominator of Trypan Blue Concentration in AC Aspirate Group

n

Mean G SD

Median

Minimum

Maximum

Group 1 Group 2

50 50

1.7 G 0.6 3.8 G 0.6

1.6 3.7

1.0 2.6

3.1 4.7

AC Z anterior chamber

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Table 5. Qualitative assessment of incision morphology features on AS-OCT after phacoemulsification by group. Number (%) 1 Day Postoperatively Parameter Epithelial gaping Endothelial gaping Localized Descemet detachment

1 Week Postoperatively

1 Month Postoperatively

Group 1

Group 2

P Value*

Group 1

Group 2

P Value*

Group 1

Group 2

P Value*

9 (18) 27 (54) 32 (64)

0 2 (4) 38 (76)

.08 .001 .44

0 12 (24) 25 (50)

0 4 (8) 30 (60)

O1.0 .04 .72

0 20 (40) 5 (10)

0 10 (20) 0

O1.0 .39 .28

*P!.05 statistically significant; Fischer exact test used

at 1 day and 1 week in Group 1 than in Group 2 (Figure 4).

However, there was a significantly greater increase in the CoV in Group 1 (PZ.03) (Table 8).

Epithelial Gaps

Central Corneal Thickness Table 8 shows the percentage change in CCT over time. The difference in the rate of change in CCT was not statistically significant between the 2 groups

At 1 week, no eye in either group showed any gaps in the epithelium. Table 6 shows the quantitative incision morphologic features. There were no significant differences in the corneal thickness 1.0 mm temporal to the incision or in the angle of incision at 1 day and 1 week between the groups. However, the incision-site thickness was slightly greater in Group 2 than in Group 1. Anterior Segment Inflammation The number of eyes having cells and flare greater than grade 2 on slitlamp examination was similar between the 2 groups (Table 7). Corneal Endothelial Morphology Three months postoperatively, the endothelial cell loss was comparable between the groups (Table 7).

Figure 3. Anterior segment OCT image showing localized Descemet detachment at the inner end of the incision.

Figure 4. Top: Optical coherence tomography image showing gaping of the incision on the endothelial side. Bottom: Misalignment of the incision on the endothelial side seen on the OCT image.

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Table 6. Quantitative assessment of incision morphology features on AS-OCT after phacoemulsification by group. Corneal Thickness 1.0 mm Temporal to Incision Postoperative Time 1 day 1 week 1 month

Group 1

Group 2

P Value

Group 1

Group 2

P Value

825.4 G 49.1 824.3 G 47.1 755.3 G 42.2

844.3 G 74.4 840 G 51.1 776.7 G 40.0

.08 .07 .08

27.17 G 4.6 26.6 G 5.0 19.6 G 6.1

23.64 G 5.15 24.56 G 5.7 20.3 G 3.7

.08 .1 .08

from preoperatively to 1 day, 1 week, or 1 month postoperatively (PO.05). Corneal Clarity Corneal clarity assessed at the slitlamp was comparable between the 2 groups at 1 day, 1 week, and 1 month (PO.05). Although not statistically significant, 40 eyes (80%) in Group 1 and 45 eyes (90%) in Group 2 had clear corneas 1 day postoperatively (PZ.23). One week postoperatively, 42 eyes (84%) in Group 1 and 47 eyes (94%) in Group 2 had clear corneas (PZ.28). The UDVA at 1 day and the CDVA at 3 months were comparable between the groups. DISCUSSION The quality of the CCI has a great impact on the outcomes after cataract surgery. The results in our study highlight that although small incisions are beneficial in phacoemulsification,1,2 maintaining wound integrity and minimizing wound distortion are the keys to securing self-sealing incisions. Often, there is clinically undetectable stretching and distortion of incisions, particularly due to manipulation with the phaco probe and IOL implantation through a tight incision. In our study, incision enlargement was significantly greater in the 1.8 mm incision group than in the 2.2 mm group. This finding is similar to that reported Table 7. Comparison of postoperative anterior segment inflammation in both groups. Number (%) Parameter Cells Rgrade 2 1 day 1 week 1 month Flare Rgrade 2 1 day 1 week 1 month

Incision Angle

Group 1

Group 2

38 (76) 35 (70) 9 (18)

42 (84) 38 (76) 10 (20)

7 (14) 6 (12) 2 (4)

8 (16) 6 (12) 1 (2)

*P!.05 statistically significant; Fischer exact test

P Value*

.31 .75 1.0 .8 O1.0 1.0

by other authors.5,6 Furthermore, similar to what Lee et al.5 reported, we found that incision stretching was greater between the initial incision and the end of phacoemulsification. Incision enlargement after IOL implantation was comparable between the groups. Interestingly, Luo et al.6 found equal enlargement in the 1.8 mm group after nucleus emulsification and after IOL implantation. In a previous experimental trial evaluating histomorphological features of the incision in rabbit eyes,A we found that when phacoemulsification was performed through a 1.8 mm incision system, there was a greater incidence of longitudinal splits in the collagen stroma with stromal irregularity, which increased after IOL implantation. This subclinical collagen damage may affect the integrity and self-sealing property of the incision. On AS-OCT, there was a greater incidence of postoperative endothelial gaping and misalignment in Group 1 at 1 day and 1 week. This finding is similar to that reported by Luo et al.,6 who found wound gap on the endothelial side in 90% of eyes with a 1.8 mm incision compared with in 75% of eyes with a 2.2 mm incision. Optical coherence tomography architectural features of endothelial gaping and loss of

Table 8. Postoperative outcomes. Parameter % change† in CCT 1 day 1 week 1 month % reduction† in ECD 3 months % change† in CoV 3 months Visual acuity (logMAR) UDVA 1 day CDVA 3 months

Group 1

Group 2

P Value*

7.48 G 7.6 5.9 G 8.3 7.63 G 9.0 5.15 G 10.2 3.44 G 7.43 2.99 G 8.6

.45 .37 .70

4.88 G 12.2 0.22 G 14.2

.35

9.59 G 9.9

0.39 G 10.2

.03

0.42 G 0.22 0.33 G 0.16 0.37 G 0.23 0.27 G 0.14

.21 .14

CoV Z coefficient of variation; CCT Z central corneal thickness; CDVA Z corrected distance visual acuity; ECD Z endothelial cell density; UDVA Z uncorrected distance visual acuity *PO.05 statistically significant † From preoperative measurement

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coaptation theoretically reduce CCI structural integrity in the immediate postoperative period. These features could represent significant risk factors for endophthalmitis. Reducing SIA is a challenge for cataract surgeons and is necessary to deliver excellent uncorrected vision postoperatively. Induced SIA was lower after phacoemulsification through the 2.2 mm incision system than through the 1.8 mm system, although not to a statistically significant degree. Surgically induced astigmatism is dependent on several variables, including incision size, incision location, incision distortion and healing. Therefore, although smaller incisions would be expected to cause lower degrees of SIA, this is not always true. It is equally important to factor in the effect of surgical maneuvers on the incision. There was no difference in the change in CCT or ECD between the 2 groups. However, the percentage change in CoV was significantly greater in Group 1, which suggests greater endothelial cell function damage. Lee et al.5 report greater endothelial cell loss with a 1.8 mm system than with a 2.2 mm system. Our findings are similar to those in previous studies,5,11,13,14 which suggest that using smaller and smaller incisions during phacoemulsification can increase the difficulty of surgery without improving clinical results. For incision sizes to become increasingly smaller during cataract surgery, it is important to have phaco tips, sleeves, and IOL delivery systems that allow phacoemulsification with minimal damage to the incision, thereby ensuring a self-sealing incision and reducing the potential for endophthalmitis. This study compared 2 popularly used platforms for microcoaxial phacoemulsification. The knives, the phaco handpiece, and ultrasound modalities were suited to each system but were different. Although both groups had IOL injection using a plunger-type injector, these injectors and cartridges were of different designs. Therefore, the differences we found in trypan ingress and incision enlargement cannot be attributed to the differences in the initial incision size alone but rather to multiple variables, including differences in energy-delivery modalities, variability in the amount of stromal hydration, and individual incision lengths apart from the above-mentioned variables. The study, therefore, provides a comparison of the 2 systems as they are being used today by surgeons worldwide. Both systems were equally efficacious in terms of postoperative outcomes in the emulsification of agerelated cataracts. In conclusion, at the end of the surgery, it is not the initial incision size alone but also the distortion of the incision during subsequent stages of surgery that determine the integrity of the CCI.

WHAT WAS KNOWN  Microcoaxial phacoemulsification is a well-established and popular technique for performing cataract surgery through small incisions. At present, it is often performed using 1 of 2 systems: 1.8 mm or 2.2 mm incision. The literature shows both to be clinically safe and efficient systems.  As incision size reduces, there are greater chances for distortion and wound damage due to instrument manipulations through tight incisions. Although studies have compared these 2 techniques in terms of clinical efficiency, incision enlargement, and OCT features of incisions, there are not much data on incision integrity in a clinical scenario using these 2 systems. WHAT THIS PAPER ADDS  In a clinical scenario, despite using compatible instrumentation, there was trypan blue ingress from the extraocular surface into the eye. However, the ingress was significantly greater when phacoemulsification was performed through a 1.8 mm incision. This was corroborated by significantly greater incision enlargement after surgery and more endothelial misalignment in the early postoperative period in the 1.8 mm group.  These findings reiterate that when using smaller and smaller incisions during cataract surgery, there is always the risk for subclinical collagen damage (mechanical and thermal) that can jeopardize incision integrity.

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OTHER CITED MATERIAL A. Vasavada V, Vasavada AR, Vasavada V, Johar KS, Sudhalkar A, Praveen MR, “Histomorphological and Immunofluorescence Evaluation of Clear Corneal Incisions following Microcoaxial Phacoemulsification Performed through 1.8 and 2.2 mm: Randomized, Experimental trial,” paper presentation at the ASCRS Symposium on Cataract, IOL and Refractive Surgery, San Diego, California, USA, March 2011 B. U.S. National Institutes of Health Clinical Trials. Outcomes Following Phacoemulsification With 1.8 & 2.2 mm Incision: Randomized Clinical Trial. NCT01385878. Available at: http://www. clinicaltrials.gov/ct2/show/NCT01385878?termZNCT01385878& rankZ1. Accessed November 16, 2012

J CATARACT REFRACT SURG - VOL 39, APRIL 2013

First author: Vaishali Vasavada, MS Iladevi Cataract & IOL Research Centre, Ahmedabad, India